This is one of the great Welsh hills, wild, remote, and in former times thought to be higher even than Snowdon. It bulks above long moorland valleys, its northern face hollowed and indented by some of the finest Welsh cwms. Llygad Rheidol – "the eye of the Rheidol" from which the dramatic, turbulent river issues on its brief course – lies right under the summit dome. Cwm Gwerin eastwardly is lonelier and finer still, one wall scoured to bare rock by glaciation, a castellated ridge on the other towering above the Afon Hengwm that drains peatlands towards Dylife. All across these brown wastes, bleached tree stumps testify to a warmer medieval climate. The peat itself plays an important role in soaking up atmospheric CO2.

By the confluence of Hengwm with Afon Hyddgen is a footbridge and a wide ledge of luxuriant grass above a deep swimming pool. I come here often, to pitch a tent and savour the silence. This time a waning moon in a clear sky glimmers across the valley flats. There is no human sound or presence. On the far hillside I can just make out white shapes of Cerrig Cyfamod Owain Glyndwr – the covenant stones of the warrior-chieftain, the first victory in whose great uprising was gained here in 1401, against massive odds. Hyddgen! – a name as significant in Welsh history as Hastings is to its English counter-narrative.

Perhaps this is the last time I shall come here. For plans are at an advanced stage to site along the skyline ridges of Hyddgen a wind factory of 64 turbines up to 146 metres high. Unless protests succeed – and there is a march near Nant y Moch reservoir tomorrow – the character of this place will be annihilated. Surely there are more fitting and expendable places for the schemes of those sensitive ones who would save the planet?